Abstract
Laser radiation has been shown to be a promising approach for in situ amorphization, i.e., drug amorphization inside the final dosage form. Upon exposure to laser radiation, elevated temperatures in the compacts are obtained. At temperatures above the glass transition temperature (Tg) of the polymer, the drug dissolves into the mobile polymer. Hence, the dissolution kinetics are dependent on the viscosity of the polymer, indirectly determined by the molecular weight (Mw) of the polymer, the solubility of the drug in the polymer, the particle size of the drug and the molecular size of the drug. Using compacts containing 30 wt% of the drug celecoxib (CCX), 69.25 wt% of three different Mw of polyvinylpyrrolidone (PVP: PVP12, PVP17 or PVP25), 0.25 wt% plasmonic nanoaggregates (PNs) and 0.5 wt% lubricant, the effect of the polymer Mw on the dissolution kinetics upon exposure to laser radiation was investigated. Furthermore, the effect of the model drug on the dissolution kinetics was investigated using compacts containing 30 wt% of three different drugs (CCX, indomethacin (IND) and naproxen (NAP)), 69.25 wt% PVP12, 0.25 wt% PN and 0.5 wt% lubricant. In perfect correlation to the Noyes–Whitney equation, this study showed that the use of PVP with the lowest viscosity, i.e., the lowest Mw (here PVP12), led to the fastest rate of amorphization compared to PVP17 and PVP25. Furthermore, NAP showed the fastest rate of amorphization, followed by IND and CCX in PVP12 due to its high solubility and small molecular size.
Highlights
In situ amorphization describes the amorphization of a crystalline drug inside the final dosage form, such as a compact [1]
It is commonly known that the viscosity and the Tg increase with the molecular weight (Mw) of the polymer [27], which results in the following order for the increase in viscosity of PVP: PVP12 < PVP17 < PVP25
The results of this study show that higher Mw of a polymer, e.g., PVP17, can be used for laser-induced in situ amorphization
Summary
In situ amorphization describes the amorphization of a crystalline drug inside the final dosage form, such as a compact [1]. In situ amorphization has been shown upon immersion in water, upon exposure to convectional heating and upon exposure to microwave and laser radiation [2,3,4,5]. Using the latter two methods, complete amorphization has been obtained [4,5,6]. Photothermal silver plasmonic nanoaggregates (PNs) [10] were shown to be a promising enabling excipient for laser-induced in situ amorphization and In order for a compact to absorb electromagnetic radiation, such as microwave or laser radiation, enabling excipients are necessary inside the compact [7,8,9].
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